Apparatus for making glass beads



Nov. 1, 1966 w. H. SEARIGHT APPARATUS FOR MAKING GLASS BEADS 2Sheets-Sheet 1 Original Filed March 22, 1962 INVENTOR. WILUAM H.SEAR|GHTBYWM ATTORNEY W. H. SEARIGHT APPARATUS FOR MAKING GLASS BEADS Nov. 1,1966 2 Sheets-Sheet 2 Original Filed March 22, 1962 INVENTOR. WILLIAM H.SEARIGHT WM A). ELM

ATTORNEY United States Patent 2 Claims. (Cl. 65-142) This is a divisionof application Serial No. 181,563, filed March 22, 1962, now abandoned.

This invention relates to the manufacture of macroscopic spherical glassbeads, such as are used, for example, for highway striping andreflective signs.

One accepted method of producing these glass beads is by feeding crushedglass into a flame so that-the glass particles are carried along withthe combustion gases and products of combustion, and during suchpassage, the glass particles are melted and due to the action of surfacetension, acquire a spherical shape. Manifestly this procedurenecessitates that the glass first be produced, and then crushed to theproper size before it can be heated and formed into spherical shapes.

An object of this invention is to produce a new and improved apparatusfor making macroscopic spherical glass beads directly from molten glass.

In accordance with this invention, glass is melted and discharged from amelting tank or collecting chamber into a plurality of relatively smallvertically descending streams arranged in annular row, the cross sectionof each stream being of the order of .0005 of one inch to one-fourth ofan inch. The glass streams while in liquid state gravitate past adispersing device which is disposed centrally thereof and from whichradiate a plurality of jets of high temperature, high velocity streamsdirected at approximately right angles to the descending streams. Thestreams may take the form of burners creating high temperature flames orjets of superheated steam or hot air. The particles of glass aredispersed by the streams and impelled laterally through a heated zonesufiiciently so that the glass particles have time to be drawn into theform of spheres by surface tension. Thereafter the particles are aircooled and collected.

For purposes of illustration, but not of limitation an apparatus forpracticing the method is shown in the accompanying drawings in whichFIGURE 1 is a somewhat diagrammatic view in vertical section of anapparatus for producing glass spheres from an annular row of relativelyfine glass streams; and

FIGURE 2 is a top plan view of the apparatus shown in FIGURE 1 with aportion of the top wall removed for purposes of clarity.

The illustrated embodiment of the invention comprises a glass meltingfurnace of any suitable form and from the furnace the molten glass flowsto a collecting chamber 11 which is formed with a hole 12 in the bottomwall. Fitting the hole 12 is an annular bushing or weir 13 which is ofplatinum or a metal or ceramic having the desired characteristics. Asshown the bushing 13 has a shoulder 14 adjacent its bottom end againstwhich a flat supporting ring 15 rests. The ring 15 .is secured inposition by a series of bolt and nut assemblies 16. The upper end of thebushing 13 is spaced above the level of the molten glass although ifdesired the molten glass may overflow the top of the bushing. Spacedslightly beneath the upper end of the bushing is an annular series oflateral passages 17, the inner ends of which open into downwardly andinwardly inclined V-shaped trough-like passages 18 arranged in anannular row, there being one of these passages for each of the lateralpassages 17. Since the lateral passages 17 are in this instance belowthe level of the molten glass, the glass can flow freely through thepassages 17 into the V-shaped trough-like passages 18. The lower end ofeach trough-like passage 18 merges into a similar shaped verticalpassage 19 which is open at its bottom end. The inclined passages 18extend somewhat over half the vertical dimension of the bushing 13. Thusit will be noted that the molten glass flows first along the inclinedV-shaped trough-like passages 18 and then vertically downward throughthe similar shaped passages 19. These passages produce an annular seriesof fine streams of glass gravitating from the upper portion of thebushing and falling freely from the bottom end thereof. Instead of thetrough-like passages, an annular row of vertical holes may be formed inthe bushing connecting at the top with the passages 17 and open at thebottom end.

It Will be understood that by varying the size of the trough-likepassages 18 and 19 and thereby controlling the diameter of the glassstreams, the size of the beads may be controlled.

The inwardly tapered form of the upper portion of the bushing formed bythe downwardly and inwardly inclined passages 18 enables the flame froma burner 20 disposed outside of the chamber 11 to project its blastthrough a tapered opening 21 and impinge upon the glass as it travelsdownwardly through the bushing 13. It is desirable that the viscosity ofthe molten stream be relatively low in order to effect proper dispersionthereof when contacted by a high velocity blast of gas as willhereinafter appear. A viscosity of the order of SAE 10 motor oil issatisfactory for this purpose. Assuming that a sodalime type of glass isused for this purpose the glass should be heated to approximately 3000F. Thus it will be manifest that the viscosity of the glass is low andis maintained at such temperature that it will flow readily.

Disposed within the annular row of glass streams gravitating from thebushing 13 is a cylindrical burner 22 which is formed with a series ofnozzles or blast openings arranged in an annular row so that the gasesfrom these openings or nozzles impinge upon the falling streams of glassand disperse the same laterally. The burner 22 is supported by apedestal 24 through which the gas and fuel are suitably conducted. Theglass streams .are thus broken into small particles or droplets ofliquid glass which almost immediately set into glass beads, sufficientheat being afforded to cause surface tension to spherulize the beads.The beads are blown generally in a lateral direction and eventually fallinto a suitable collecting chamber 25. A substantial free fall in spaceof the beads is provided by the positioning of the collecting chamber,thereby providing for a sufficient setting time during the vertical fallof the beads.

The burner 22 may be of any suitable type characterized by the burningWithin a combustion chamber a combustible mixture of gas, air, oxygen,etc. the products of combustion being discharged through the restrictedports as a high velocity jet or blast. In the form shown the blast ofgases discharged may be at a temperature of approximately 3l00 F. and avelocity of approximately 1000 feet per second.

Numerous changes in details of construction, arrangement and operationmay be effected without departing from the spirit of the invention,especially as defined in the appended claims.

What I claim is:

1. Apparatus for forming glass beads comprising:

means for gravitating a plurality of discrete glass streams of lowviscosity arranged in an annular row; means for directing a plurality ofradially extending jets of high velocity heated gases normally againstthe direction of flow of said glass streams, said jets of high velocityheated gases being in numerical correspondence to said glass streams,said jets thereby causing said glass streams to be dispersed into amulti- I plicity of glass particles; and

annular chamber means surrounding said jet directing means in spacedrelation to provide a suspension zone wherein said particles arespherulized and fall into a lower temperature zone to be collected.

2. Apparatus for forming glass beads as claimed in claim 1 in which saidgravitating means comprises a bushing having a vertical openingsurrounded by an annular row of V-shaped channels, the upper portions ofthe channels inclining inwardly and downwardly and the lower portionsbeing vertically disposed, and a burner for directing a heated blastagainst the inclined upper channel portions.

References Cited by the Examiner UNITED STATES PATENTS DONALL H.SYLVESTER, Primary Examiner.

G. R. MYERS, Assistant Examiner.

1. APPARATUS FOR FORMING GLASS BEADS COMPRISING: MEANS FOR GRAVITATING APLURALITY OF DISCRETE GLASS STREAMS OF LOW VISCOSITY ARRANGED IN ANANNULAR ROW; MEANS FOR DIRECTING A PLURALITY OF RADIALLY EXTENDING JETSOF HIGH VELOCITY HEATED GASES NORMALLY AGAINST THE DIRECTION OF FLOW OFSAID GLASS STREAMS, SAID JETS OF HIGH VELOCITY HEATED GASES BEING INNUMERICAL CORRESPONDENCE TO SAID GLASS STREAMS, SAID JETS THEREBYCAUSING SAID GLASS STREAMS TO BE DISPERSED INTO A MULTIPLICITY OF GLASSPARTICLES; AND ANNULAR CHAMBER MEANS SURROUNDING SAID JET DIRECTINGMEANS IN SPACED RELATION TO PROVIDE A SUSPENSION ZONE WHEREIN SAIDPARTICLES ARE SPHERULIZED AND FALL INTO A LOWER TEMPERATURE ZONE TO BECOLLECTED.